1,720,983 research outputs found
Molecular investigations in western Palearctic water frogs
No full textIn the green frog hybrids there exists an exclusive cytogenetic reproductive mechanism, referred to as hybridogenesis, whoseevolutionary value is still under debate. As a contribution to the knowledge of the possible link between reproductive strategies and phylogenetic relationships, the analysis of repetitive DNA elemento in the genomes of the Balkan green frogs, Rana epeirotica and R. shqiperica was carried out to compare their molecular DNA organization with those already known for R. ridibunda and R. lessonae. The Balkan species were chosen, because they give rise to spontaneous, although infrequent and not hybridogenetic
hybrids with R. ridibunda. The elements of the RrSl family, a centromeric satellite DNA previously isolated in R. ridibunda, are clustered at centromeric regions also in both Balkan species, although the molecular organization of the RrSl sequences proved to be most similar in R. ridibunda and R. epeirotica. Furthermore,
a repetitive DNA family (R1BamHI) is interspersed throughout the genome and is highly conserved in all species examined. Notably, the RIBamHI sequences, correlated to members of the hAT famil, represent the first transposable elements found in the genus Rana. In the light of the results obtained so far, further studies are in
progress with the aim of isolating and characterizing new families of repeated DNA, as additional results are required to compare the genomes of the different frog species and infer phylogenetic deductions on the genome evolution accompanying the speciation process and occurring inside the Palearctic green frog system
Isolation and expression of RlYB2, a germ cell-specific Y-box gene in Rana
No full textY-box proteins are a highly conserved family of gene expression regulatory factors. During gametogenesis they may play a dual role, as both transcriptional activators of germ cell-specific genes and as translational repressors of stored maternal transcripts. We report the identification of RlYB2, a Y-box homolog gene specifically expressed in the germ cells of green frogs belonging to Rana esculenta complex, a model system characterized by a hybridogenetic gametogenesis. In developing germ cells of the hybrid R. esculenta, arisen by natural cross of the parental species R. ridibunda and R. lessonae, one set of the parental genomes is excluded and the remaining one, first endoreduplicates and then is transmitted to gametes. In situ hybridizations performed on gonadal tissues showed that the RlYB2 transcript was widely expressed in the ooplasm at early stages of oogenesis in both the parental species and hybrids. Interestingly, a hybridization signal, presumably related to RlYB2-like nascent transcripts, was observed in nuclei of stage II oocytes. The presence of RlYB2 mRNA during early oogenesis suggests that this gene may be involved in regulating the transcription and/or translation of maternal mRNAs in this special vertebrate model system
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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